1. Field of the Invention
This invention relates to electrophotographic photosensitive members and more particularly to an electrophotographic photosensitive member having a charge transport layer or photosensitive layer which contains a specific hydrazone compound.
2. Description of the Prior Art
There have so far been known inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide. In contrast to their many advantages, for instance, chargeability to a suitable potential in a dark place, less dissipation of charge in a dark place, and fast dissipation of charge possible by light irradiation, these photoconductive materials have also some disadvantages. For instance, selenium group photosensitive members have the disdvantages of a difficulty in setting manufacturing conditions and of a consequent high manufacturing cost, and in addition are deficient in flexibility, heat stability, and physical strength. Zinc oxide group and cadmium sulfide group photosensitive members are unsatisfactory in physical and mechanical properties such as surface smoothness, strength, and wear resistance, because these photosensitive materials are used in the form of dispersion in a binder resin. Zinc oxide group photosensitive member, requiring sensitization with coloring matter, of which a typical one is Rose Bengal, are also disadvantageous in that they cannot provide stable images over a long period of survice because said coloring matter causes charge deterioration due to corona charging or light fading due to exposure.
On the other hand, various organic photoconductive polymers including polyvinylcarbazole have been proposed. However, they have been prevented from practical use until now in spite of their superiority to inorganic photoconductive materials, mentioned above, in film-forming capability and lightness. This is because the organic photoconductive polymers hitherto proposed do not have sufficient sensitivity and are inferior to the inorganic photoconductive materials in durability or stability to environmental variations.
Further, there are known photosensitive members employing a low-molecular organic photoconductive substance such as p-diethylaminobenzaldehyde-N,N-diphenylhydrazone or p-diethylaminobenzaldehyde-N-phenyl-N-benzylhydrazone, disclosed in U.S. Pat. No. 4,150,987 (Jpn. Pat. Appl. Laid-open No. 59143/1979), N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole disclosed in Ger. Pat. Offen. No. 291971 (Jpn. Pat. Appl. Laid-open No. 150128/1979), p-diethylaminobenzaldehyde-N-phenyl-N-methylhydrazone disclosed in Jpn. Pat. Appl. Laid-open No. 52064/1980. Low-molecular organic photoconductive substances have the advantage of being capable of forming a good film of photosensitive layer in combination with an appropriate binder resin. In practice, however, the electrophotographic photosensitive members employing these hydrazone compounds are still unsatisfactory in sensitivity or in the stability of light portion potential when charging and exposing are repeated, thus requiring further improvements.